Letter to the editor

Folic acid and human malformations:misunderstandings

To the Editor:The objective of special article written by H. Kalter

(Reprod Toxicol 2000;14:463–476) was to present argu-ments against the well-accepted primary preventive effectof periconceptional folic acid supplementation for neural-tube defects (NTD), because it discussed the weak points ofthis concept. However, the objective was impaired by somemisunderstandings and wrong citations.

First of all, according to the internationally used classi-fication of NTD [1], this congenital abnormality entity in-cludes anencephalus, spina bifida aperta (spina bifida cys-tica or rachischisis these terms are synonyms and includethe lesion of the spinal cord), encephalocele, and craniora-chischisis (i.e., anencephalus and spina bifida together). Ingeneral, anencephalus and so-called spinal dysraphism arealso included in this abnormality entity. However, spinabifida occulta (when only one vertebra is affected and thereare no associated abnormalities) is excluded. Spina bifidaaperta/cystica is classified according to location (e.g., cer-vical, thoracic, lumbar) and manifestation: meningomyelo-cele, meningocele, etc. Thus, it is a serious misunderstand-ing that spina bifida aperta/cystica is not part of NTD. TheInternational Classification of Diseases [2] differentiatesspina bifida with or without hydrocephalus. From an etio-logic aspect, it is worth separating so-called isolated andsyndromic NTDs; the latter may involve NTD and othermajor congenital abnormalities caused by chromosomal ab-errations (e.g., trisomy 18), gene mutations (such as Meckelsyndrome), and teratogenic agents (valproic acid effect).Thus, Dr. Kalter probably confuses the terms spina bifidacystica and spina bifida occulta.

There was a wrong citation concerning the Hungarianbirth/total prevalence of NTD. We used several approachesin determining this rate. The first and major approach wasan ad hoc epidemiologic study in which all sources ofpossible cases with NTD were ascertained in the 1960s andthe birth prevalence was 2.95 per 1000 total births [3]. Afterthe exclusion of syndromic NTD, the birth prevalence ofNTD was 2.78 per 1000 total births. Nevertheless Dr. Kalterwrote: “Hungary in the 1980s was a relatively low-risk area,the total prevalence of NTD including all births and prena-tally diagnosed and terminated fetuses, being about 1 per1000.” This statement is based on my review paper [4], but

without the continuation of my text: “However, this rate isan underascertainment because several anencephalics diag-nosed prenatally were not notified.” In our randomiseddouble-blind controlled trial the total prevalence of NTDwas 2.51 per 1000 in the placebo-like group [5]. In ourrecent controlled cohort study there were 8 informativeoffspring with NTD among unsupplemented control off-spring giving a total prevalence of 2.62 per 1000 [6]. ThusHungary is a moderate-risk area for NTD and cannot beused to question the results of the MRC Vitamin Study, asDr. Kalter stated, because 42.3% (769/1817) of randomisedwomen were recruited in the 7 Hungarian centers.

There is a complete misunderstanding in connectionwith the Hungarian randomised double-blind controlledtrial, which was a single study to check the efficacy of amultivitamin-mineral-trace element compound (Elevitpronatalt) containing 0.8 mg folic acid in the primaryprevention offirst occurrence of NTD. The double-blind-edness of the trial was questioned because in 1989 I wasforced by authorities to break the code due to the possibleteratogenic risk of the Vitamin A component (6000 I.U.)of Elevit pronatal® used in the 1980s. However, mycoworkers in the trial, who met participants and evalu-ated pregnancy outcomes, were not informed of the con-tent of the two study preparations and thus remainedblinded. In Hungary, periconceptional care was estab-lished in 1984; therefore, it was easy to integrate this trialinto this medical service. The start of this care is 3months before the planned conception; thus, the pericon-ceptional supplementation was part of the 3-month pre-paratory period for conception. As Table 1 shows, we had7905 participants who were eligible and voluntarilyjoined the trial during the study period. Thus they werenot pregnant, as was stated by Dr. Kalter. Of these 7905randomised women, 5502 had pregnancies within oneyear, confirmed by pregnancy test and/or ultrasound inthe third through fifth postconceptional week. The num-ber ofevaluatedpregnancies was 5453 due to the dropoutof 49 women (0.9%). Unfortunately, 460 (8.4%) womendid not follow the recommendation of periconceptionalsupplementation and were classified as unsupplemented.However, the trial was a randomised clinical study – notan animal experiment – therefore the different compli-ance of individual subjects was similarly distributed be-tween the two randomised groups. On the other hand,evaluation of informative offspring followed intention-

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to-treat analysis. In Dr. Kalter’s article, the followingsentence is a very serious misunderstanding: “. . . unto-ward pregnancy outcomes during the first trimester werenot monitored.” Just the opposite, our trial provided aunique occasion for the monitoring of all possible preg-nancy outcomes during the first trimester, because theconception was planned and the pregnancy was diag-nosed as soon as possible; therefore, we were able torecognise very early fetal loss as well. The fetal deathgroup included four subgroups (Table 1), e.g., the so-called chemical and ectopic pregnancies, which could notbe evaluated in other studies. Of course, there were noexaminable zygotes or embryos in these pregnancy out-comes. A further general misunderstanding concerns theevaluation of spontaneous abortions (miscarriages). Ingeneral, these pregnancy losses were completed by cu-rettage; therefore, the embryo was destroyed. In addition,40.2% and 38.2% of spontaneous abortions were so-called missed abortions (or blighted ova) in the multivi-tamin and placebo-like trace element groups, respec-tively; thus, there wasno embryo for examination. Thenew term, informative pregnancies in the MRC VitaminStudy and informative offspring in the Hungarian Trial,was introduced because only three pregnancy outcomes,liveborn infants, stillborn fetuses, and prenatally diag-nosed and terminated fetuses, were appropriate for tera-tologic examination. We used the term informative off-spring instead of informative pregnancies due to multiplepregnancies because the denominator of our trial was notpregnant woman, but fetus-newborn infant. In the trialthere were no and six informative offspring with NTD inthe multivitamin and placebo group, respectively (P 50.01). In the final report of the trial, NTD offspring werenot listed because the goal of this paper was to demon-strate pregnancy outcome, but the details on NTD off-spring were shown in other papers e.g., [5]. I show them

here in Table 2. It was a great help for us that the U.S.Centers for Disease Control organised a Scientific Advi-sory Committee for the trial including T.C. Chalmers(Boston), J.D. Erickson (Atlanta), F.S. Fraser (Montreal),L.B. Holmes (Boston), and R.W. Smithells (Leeds) whovisited us and checked our trial, particularly cases withNTD. There was full agreement in their diagnosis. Forthe sake of accuracy, Dr. Erickson organised anotherspecial evaluation of NTD offspring with the participa-tion of experts from the International Clearinghouse forBirth Defects Monitoring Systems, again with perfectagreement.

In conclusion, I must refuse the conclusion of Dr. Kalter:“Therefore, all in all, the conclusion of the study, that ‘thisprimary preventive method can reduce the occurrence’ ofNTD, cannot be accepted as proven. This situation com-pounds the doubt regarding the outcome of the MedicalResearch Council Trial [63] described above, because over40% of the subjects of that study were of Hungarian origin.”The latter sentence again is a misunderstanding because thedesign of the MRC Vitamin Study was entirely different.

I hope that other counterarguments in the paper of Dr.Kalter have a more solid basis. Finally, it was a disappoint-ment for me that the possible prevention of cardiovascularand urinary tract abnormalities, in addition limb deficien-cies, was not mentioned in a paper entitled, “Folic acid andhuman malformations” because a number of papers havebeen published on this aspect [7–14] beyond the cited paperof Werler et al.

Andrew E. Czeizel M.D.Foundation for the Community of Hereditary Diseases,

Budapest, HungaryH-1026, Torokvesz lejto32.

Tel./Fax:136-1/394-4712

Table 1The data set and pregnancy outcomes of the Hungarian trial

Data set Multivitamin Trace element

(N) (%) (N) (%)

Number of participants 3953 100.0 3952 100.0Pregnant women 2819 71.3 2683 67.9Dropouts 26 0.9 23 0.9Evaluated pregnancies 2793 100.0 2660 100.0Termination

First trimester 6 0.2 6 0.2Second trimester 3 0.1 13 0.5Subtotal 9 0.3 19 0.7Fetal deathChemical pregnancy 55 2.0 40 1.5Ectopic pregnancy 7 0.2 4 0.2Miscarriage 301 10.8 251 9.4Stillbirth 11a 0.4 9 0.3Subtotal 374 13.4 304 11.4

Livebirths 2410 86.3 2337 87.9

aThree stillbirths occurred in twin pregnancies in which the other twin was liveborns

442 Letters to the Editor / Reproductive Toxicology 15 (2001) 441–444

References

[1] Nevin NC, Weatherall JAC. Illustrated Guide to Malformations of theCentral Nervous System at Birth. Edinburg: Churchill Livingstone,1983.

[2] WHO. International Classification of Diseases. Xth ed. Geneva, 1993[3] Czeizel AE, Re´vesz C. Major malformations of the central nervous

system in Hungary. Br J Prev Soc Med 1970;24:205–22.[4] Czeizel AE. Epidemiological studies of congenital abnormalities in

Hungary. In: Kalter H, editor. Issues and Reviews in Teratology. NewYork: Plenum, 1993. p. 85–124.

[5] Czeizel AE. Periconceptional folic acid containing multivitamin sup-plementation. Eur J Obstet Gynecol Reprod Biol 1998;78:151–1.

[6] Czeizel AE. Primary prevention of neural-tube defects and someother major congenital abnormalities. Pediatr Drugs 2000;2:1–14.

[7] Czeizel AE. Prevention of congenital abnormalities by periconcep-tional multivitamin supplementation. Brit Med J 1993;306:1645–8.

[8] Czeizel AE. Reduction of urinary tract and cardiovascular defects bypericonceptional multivitamin supplementation. Am J Med Genet1996;62:179–3.

[9] Li DK, Daling JR, Mueller B, et al. Periconceptional multivitamin usein relation to the risk of congenital urinary tract anomalies. Epide-miology 1995;6:212–8.

[10] Shaw GM, O’Mulley CD, Wasserman CR, et al. Maternal pericon-ceptional use of multivitamins and reduced risk for conotruncal heartdefects and limb deficiencies among offspring. Am J Med Genet1995;59:536–45.

[11] Botto LD, Khoury MJ, Mulinare J, et al. Periconceptional multivita-min use and the occurrence of conotruncal heart defects. Results froma population-based case-control study. Am J Med Genet 1995;59:536–45.

[12] Yang Q, Khoury MJ, Olney RS, et al. Does periconceptional multi-vitamin use reduce the risk for limb deficiency in offspring? Epide-miology 1997;8:157–61.

[13] Werler MW, Hayes C, Louik C, et al. Multivitamin use and risk ofbirth defects. Am J Epidemiol 1999;150:675–82.

[14] Botto LD, Mulinare J, Erickson JD. Occurrence of congenital heartdefects in relation to maternal multivitamin use. Am J Epidemiol2000;151:878–84.

In Reply:

In the several months since my article on folic acid andhuman malformations was published, only Czeizel has writ-ten to question statements in it. He notes two matters.

The first regards the definition of “spina bifida cystica.”According to a higher authority than the one he cites, theterm is a generic one, pertaining to a midline lesion of theosseous spine consisting of an external saccular protrusion,which contains either meninges but no neural elements, orspinal cord, and nerves. The name for the former is menin-gocele, and for the latter, myelomeningocele. Thus, theformer, as I stated elsewhere in the article in question, is nota true neural tube defect. If, therefore, when a statement ismade that “spina bifida cystica” occurred, it is not sufficientto prove that the condition was a neural tube defect withoutfurther documentation that the lesion contained elements ofthe spinal cord.

Czeizel concludes by saying, “Thus, Dr. Kalter probablyconfuses the terms spina bifida cystica and spina bifidaocculta.” But it is not me but he who is confused, since inhis review of epidemiologic studies of congenital abnormal-ities in Hungary (his citation number 4), he himself equates

Table 2The number and rate (per 1000 informative offspring) of some major congenital abnormalities

Abnormality Trace elementsupplementation(N 5 2391)

Multivitaminsupplementation(N 5 2471)

Odds ratio (95% Confidence interval)

(N) Rate (N) Rate

IsolatedNeural-tube defects 6 2.51 0 0.00 0.06 (0.00–0.63)

Anencephalus 2 0.84 0 0.00 – –Spina bifida cystica

(thoracolumbar, sacral)2 0.84 0 0.00 – –

Anencephalus1 spinabifida cystica

2 0.84 0 0.00 – –

Urinary tract defects 9 3.76 2 0.81 0.21 (0.05–0.99)Obstructive and renal

agenesis8 3.35 1 0.40 0.12 (0.02–0.69)

Cardiovascular defects 20 8.26 10 4.05 0.42 (0.19–0.98)Conotruncal 10 4.18 3 1.21 0.29 (0.09–0.97)

Limb deficiencies 5 2.09 1 0.40 0.19 (0.03–1.18)Hypertrophic pyloricstenosis

8 3.35 2 0.81 0.24 (0.05–1.14)

Orofacial defects 5 2.09 4 1.62 0.77 (0.22–2.69)Cleft lip 1 palate 3 1.25 4 1.62 1.29 (0.32–5.22)Cleft palate 2 0.84 0 0.00 0.19 (0.01–4.03)

Other abnormalities 33 13.80 22 8.90 0.64 (0.37–1.10)Multiple abnormalities 11 4.60 10 4.05 0.88 (0.37–2.07)Total 97 40.57 51 20.64 0.53 (0.35–0.70)All without neural-tube defects 91 38.06 51 20.64 0.53 (0.38–0.75)

443Letters to the Editor / Reproductive Toxicology 15 (2001) 441–444